The present invention generally relates to heating apparatus and, in a preferred embodiment thereof, more particularly relates to a specially designed outside combustion air intake hood structure for a fuel-fired, direct vent water heater.
A fuel-fired water heater is typically installed in an interior building space and, during operation of the water heater, discharges combustion gases through a vent stack to the exterior of the building while at the same time receiving outside combustion air via a suitable air inlet duct communicated with its combustion chamber. A direct vent water heater induces the requisite flow of outside combustion air through this air inlet duct by the natural draft stack effect (created by the burning of a fuel-air mixture within its combustion chamber) thereby eliminating the need for any forced draft equipment (such as a draft inducer fan) and any associated power requirement. While the use of natural combustion draft in place of, for example, a draft inducer fan to flow outside air into the water heater's combustion chamber desirably lessens the overall cost of the water heater, it often poses a design challenge relating to the prevention of undesirable fluctuations in the pressure of combustion air being delivered to the water combustion chamber.
Specifically, an air intake hood is typically mounted on the outer surface of an outside wall and connected to the combustion air inlet duct. The air intake hood is needed to protect the combustion air duct inlet from contamination while permitting sufficient air flow into the water heater combustion chamber. When the wind blows in a direction perpendicular to the duct inlet (e.g., parallel to the outside wall upon which the intake hood is mounted) at high speed, a negative pressure is created at the air duct inlet which correspondingly creates a more negative pressure in the combustion chamber which may snuff out the burner flame or at least deprive it of sufficient combustion air. Similarly, when a strong wind is blowing generally toward the outside wall upon which the intake hood is mounted, an undesirably high pressure may be created within the water heater combustion chamber.
As can be readily seen from the foregoing, a need exists for an improved combustion air intake hood structure, for a water heater or other types of fuel-fired direct vent heating appliances, in which the combustion air inlet duct pressure variations caused by changes in outside wind directions is substantially lessened. It is to this need that the present invention is directed.